1. Field of the Invention
This invention relates generally to cold or field emission cathode relativistic magnetron devices.
2. Description of Related Art
The conventional magnetron is a well-known and very efficient source of low frequency microwaves. Its operating principles have been known since at least 1921, and the first pulsed resonant cavity magnetron (3 GHz), built by the British in 1940, can be considered the germinal point of modern microwave radar. Today, magnetrons can be found in every home possessing a microwave oven.
A typical single body magnetron is a coaxial vacuum device consisting of an external cylindrical anode (the positive electrode, which attracts electrons) and an internal, coaxial cylindrical cathode (the negative electrode, which emits electrons). In many designs, rectangular resonator cavities are cut into the anode block in a gear tooth pattern. During operation, a constant axial (perpendicular to the plane of the page) magnetic field fills the vacuum annulus, and an electric potential is placed between the anode and cathode. The number and shape of the resonator cavities, and the dimensions of the anode and cathode are arbitrary design features which determine the magnetron's frequency and operating characteristics.
Deficiencies in the present high power microwave magnetron technology are evident, with the most serious being the inability to generate pulse lengths of a microsecond or greater. This is particularly critical for increasing the energy per pulse being produced. A magnetron producing 500 MW for 3 .mu.s would represent an order-of-magnitude increase in energy per pulse over the present experimental devices, and is greatly desired for practical applications.
Attempts have been made in the past to achieve higher output power by phase locking separate magnetrons. However, magnetrons are historically notorious for their inability to be phase locked. Efforts are being made to achieve injection phase locking of several distinct or separate magnetron bodies having a common master input signal. Efforts have also been made to achieve bootstrap phase locking of several distinct magnetron bodies arranged side by side in a hexagonal array by energizing them simultaneously without a common master input signal, but with pair-wise waveguide connections between the magnetrons. The communication between the magnetron bodies via the waveguides is tenuous at best in this arrangement, and neither approach can be considered a significant solution to the phase-locking problem.